Jan.
12, 2007 — Skiers, sledders and snowmobilers in the central U.S. and
East have been left itching for snow this season as El
Niño influences the nation's typical winter weather pattern.
In Thursday’s daily
snow analysis issued by NOAA,
only 26 percent of the contiguous U.S. is currently covered by snow—with
the greatest aerial coverage and depths across the higher elevations
of the West and with relatively paltry amounts in the upper Midwest
and Northeast. (Click NOAA snow depth image for larger view
showing national conditions across the USA on Jan. 11, 2007. Please
credit “NOAA.”)

"The
distribution of snow across the country so far this season has been
uneven, to say the least. While some areas have been inundated with
snowfall, others are lacking," said Don Cline, PhD., acting director
of the NOAA National Operational
Hydrologic Remote Sensing Center in Chanhassen, Minn. Even NOAA's
snow scientists in Chanhassen are currently contending with bare ground
and a seasonal snowfall currently 20 inches below average.

So
far this season, the jet stream—the river of fast-moving air in
the upper levels of the atmosphere—has largely flowed in a west
to east "zonal" direction near the northern tier of the country.
This has escorted milder Pacific air across the country while locking
arctic air in Canada. (Click NOAA snow depth image for larger
view showing national conditions across the USA on Jan. 12, 2005. Please
credit “NOAA.”)

At times,
the jet stream has dipped south, especially over the western U.S., allowing
colder air to invade. When this cold air combines with moisture, heavy
snow has been the byproduct over the Intermountain West, Colorado and
High Plains. When the jet stream dips south over the West, it often
shifts north of its normal position in the East, resulting in abnormally
warm conditions over the eastern half of the country and supporting
rain as the predominate form of precipitation.

Nationally,
the current 26 percent snow coverage is on par to the coverage this
day last year, but is much less than the 43 percent in 2005 and 33 percent
in 2004.

Regionally,
the Northeast had extensive snow cover in December and January during
the past three seasons with 90 percent to 100 percent snow coverage
much of the period and occasional decreases to around 50 percent. This
year, snow cover has been much lower with much of December down to 10
percent to 15 percent, and topping out at less than 80 percent.

In the
northern Great Lakes region, December started with close to 90 percent
snow cover but then dropped down to about 30 percent by mid-December.
Currently, the Upper Midwest has a little less snow cover than this
time over the past three seasons.

In contrast,
much of the West has been experiencing frequent snow storms resulting
in extensive snow cover. Most notably, the central Rocky Mountains of
Colorado and Wyoming currently have 90 percent to 100 percent snow cover,
compared to 50 percent to 80 percent snow cover at this time during
the past three years.

"This
is still a young winter season, and it takes just a single storm to
drop a fresh blanket of snow and chip away at mounting snowfall deficits,"
Cline added. He recalled the light amount of snow in January of last
year in parts of the East, which was followed by an early February storm
that dumped up to 28 inches of snow from the Carolinas to New England.

NOAA, an
agency of the U.S. Commerce Department,
is celebrating 200 years
of science and service to the nation. From the establishment of
the Survey of the Coast in 1807 by Thomas Jefferson to the formation
of the Weather Bureau and the Bureau of Commercial Fisheries in the
1870s, much of America's scientific heritage is rooted in NOAA. NOAA
is dedicated to enhancing economic security and national safety through
the prediction and research of weather and climate-related events and
information service delivery for transportation, and by providing environmental
stewardship of the nation's coastal and marine resources. Through the
emerging Global Earth Observation System of Systems (GEOSS),
NOAA is working with its federal partners, more than 60 countries and
the European Commission to develop a global monitoring network that
is as integrated as the planet it observes, predicts and protects.